A conventional virtual-machine monitor (VMM) typically runs on a computer and presents to other software the abstraction of one or more virtual machines. Each virtual machine may function as a self-contained platform, running its own “guest operating system” (i.e., an operating system (OS) hosted by the VMM) and other software, collectively referred to as guest software. The guest software expects to operate as if it were running on a dedicated computer rather than a virtual machine. That is, the guest software expects to control various events and have access to hardware resources such as physical memory and memory-mapped input/output (I/O) devices. For example, the guest software expects to maintain control over address-translation operations and have the ability to allocate physical memory, provide protection from and between guest applications, use a variety of paging techniques, etc. However, in a virtual-machine environment, the VMM should be able to have ultimate control over the computer's resources to provide protection from and between virtual machines.